Re: 2003 Ford Windstar SE - Low MPG
As you recently bought it, did it come with any previous maintenance records? If not, your best bet is to spend a couple hundred bucks here and change out the transmission fluid, as well as take it in to have a tune up performed (new plugs, etc). Also make sure the tires are inflated properly. You can run tires at 20psi (instead of say 34), and the tire will look properly inflated but will cut 15-30% off of your mileage.
If in doubt, change out the air filter anyway. For $6 or so, you can't go wrong, and it's better piece of mind. It's fairly straight forward to change it out yourself.
Depending on the miles, you should do what Bert mentioned, and clean the MAF sensor. Inside the air intake tube can get very dirty overtime and put a film of dust/dirt on the sensor wire(s) which will give an incorrect air-to-fuel reading to the engine. This too is easily done if you have a large zip lock bag, and some basic tools. The MAF is located just before the throttle body, at the end of the air intake tube. You'll have to disconnect the plug going to the sensor, throw some MAF cleaner in the bag and shake the sensor around in the bag for a minute just being careful not to damage the wire(s) inside the tube. Then reinstall. An aerosol MAF cleaner can work also, and can be less messy.
'11 Ram Quad Cab 4x4 SXT 5.7L HEMI (stock); 48,500m
'06 Pontiac G6 GT 3.5L 220hp; 64,000m
'12 Chrysler 200 Limited 3.6L 283hp; 28,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!